Heat-treatment for high carbon high chromium steel



Patented Oct. 25, 1949 HEAT-TREATMENT FOR HIGH CARBON HIGH CHROMIUMSTEEL Carroll G. Hoffman, Independence, and John M. Kiefer, Jr., EastCleveland, Ohio, assignors to The American Steel and Wire Company of NewJersey, a corporation of New Jersey No Drawing. Application April 24,1946, Serial No. 664,694

4 Claims.

This invention relates to high carbon high chromium steels and moreparticularly to thermal treatments for such steels.

The use of high carbon high chromium steels of the class containing from.5 to 1.25 per cent carbon and 10 to 16 per cent chromium, manganese ineffective amounts but not over 1.10 per cent, .25 per cent maximumnickel, normal amounts of phosphorus, sulphur and silicon and thebalance substantially iron except for residual amounts of otherelements, has heretofore been restricted because of their extremebrittleness at room temperature. A typical analysis of a steel withinthis class is about 1 per cent carbon, 14 per cent chromium, and .80 percent manganese. Such a steel is generally considered martensitic.

By treating such steels as the foregoing in accordance with theteachings of our invention, as hereinafter described, it becomespossible to cold process them after being hot rolled or forged.Ordinarily such steels cannot be further processed to any great extentby cold rolling or other deforming at or near room temperature becauseof their extreme brittleness. In part, this brittleness, which resultsin fracturing of the steel upon very slight deformations at or near roomtemperature, is the result of excessively large, usually angular,carbides formed during the solidification and cooling of the steel.These carbides may increase in size during the hot working heatingoperations.

In accordance with the teachings of our invention, such steels can beannealed and rendered suitable for cold deformation in the followingmanner. Articles of steel of the specified composition are heatedpreferably to between 50 and 75 F. below the melting range of the steel,or to from 2100 to 2250 F. and held at such temperature between fifteenminutes and four hours. The steel is then cooled in a relatively rapidmanner to below 1000 F., either in air or in liquid, but in any case ata rate of at least 50 per hour.

The steel is then reheated to within the temperature range of 1250 to1500 F. for an interval of between four and twenty-four hours andpreferably cooled in any convenient manner to substantially roomtemperature. Such cooling should exceed at least 25 per hour.

Either after such a cooling to substantially room temperature ordirectly from a temperature in the range of 1250 to 1500 F. the steel isheated to a temperature of 1650 to 1700 F. for from fifteen minutes toeight hours and then cooled in any suitable manner, which does not formcoarse carbides, but which must be in excess of 25 F. per hour,preferably to Within but not below the temperature range of 1250 to 1450F.

The final step in our treatment is holding the steel within thetemperature range of 1250 to 1450 F. for from four to twenty-four hoursfollowed by cooling to room temperature in any manner desired.

These heating steps cause a series of phase or constituent changes ortransformations of the steel, which must follow one another in thecorrect sequence to produce the final desired type of phase orconstituent aggregate having the desired properties for cold working.Therefore, it is an essential feature of the foregoing heatingoperations that they be performed in the sequence described in order toobtain the desired ductility and quality of being cold-deformable.

While we have described certain specific embodiments of our invention,it will be understood that these embodiments are merely for the purposeof illustration and description and that various other forms may bedevised within the scope of our invention, as defined in the appendedclaims.

We claim:

1. A method of producing cold-deformable high chromium alloy steelcontaining between .5 and 1.25 per cent carbon, 10 to 16 per centchromium, manganese in effective amounts up to 1.10 per cent; not over.25 per cent nickel and balance substantially iron comprising heatingsaid alloy steel to a temperature between 2100 and 2250 F., holding atsaid temperature for between fifteen minutes and four hours, rapidlycooling from such temperature to below 1000 F. at a rate of at least 50per hour, heating to within the range of 1250 to 1500 F., holding insuch range for a time between four and twenty-four hours, reheating to atemperature within the range of 1600 to 1750" F., holdingat suchtemperature for from fifteen minutes to eight hours, cooling to Withinthe range of from 1250 to 1450 F. at a rate in excess of 25 per hour andholding in such range for from four to twenty-four hours.

2. A method of producing cold-deformable high chromium alloy steelcontaining between .5 and 1.25 per cent carbon, 10 to 16 per centchromium, manganese in effective amounts up to 1.10 per cent, not over.25 per cent nickel and balance substantially iron comprising heatingsaid alloy steel to a temperature within 50 to F. below the meltingrange of the steel, holding at said temperature for between fifteenminutes and four hours, rapidly cooling from such temperature to below1000 F. at a rate of at least 50 per hour, heating to within the rangeof 1250 to 1500 F., holding in such range for a time between four andtwenty-four hours, reheating to a temperature within the range of 1600to 1750 F., holding at such temperature for from fifteen minutes toeight hours, cooling to within the range of from 1250 to 1450 F. at arate in excess of 25 per hour and holding in such range for from four totwenty-four hours.

3. A method of producing cold-deformable high chromium alloy steelcontaining between .5 and 1.25 per cent carbon, to 16 per cent chromium,manganese in effective amounts up to 1.10 per cent, not over .25 percent nickel and balance substantially iron comprising heating said allo;steel to a temperature between 2100 and 2250 F., holding at saidtemperature for between fifteen minutes and four hours, rapidly coolingfrom such temperature to below 1000 F. at a rate of at least 50 perhour, heatin to within the range of 1250 to 1500 F., holding in suchrange for a time between four and twenty-four hours, cooling tosubstantially room temperature at a rate in excess of 25 per hour,reheating to a temperature within the range of 1600 to 1750 F., holdingat such temperature for from fifteen minutes to eight hours, cooling towithin the range of from 1250 to 1450 F. at a rate in excess of 25 perhour and holding in such range for from four to twenty-four hours.

4. A method of producing cold-deformable high chromium alloy steelcontaining between .5 and 1.25 per cent carbon, 10 to 16 per centchromium, manganese in effective amounts up to 1.10 per cent, not over.25 per cent nickel and balance 4 substantially iron comprisin heatingsaid alloy steel to a temperature within to F. below the melting rangeof the steel, holding at said temperature for between fifteen minutesand four hours, rapidly cooling from such temperature to below 1000 F.at a rate of at least 50 per hour, heating to within the range of 1250to 1500 F., holding in such range for a time between four andtwenty-four hours, cooling to substantially room temperature at a ratein excess of 25 per hour, reheating to a temperature within the range of1600 to 1750" F., holding at such temperature for from fifteen minutesto eight hours, cooling to within the range of from 1250 to 1450 F. at arate in excess of 25 per hour and holding in such range for from four totwentyfour hours.

CARROLL G. HOFFMAN. JOHN M. KIEFER, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,188,155 Payson Jan. 23, 19402,363,736 Lynn Nov. 28, 1944 OTHER REFERENCES Transactions of theAmerican Society for Metals, vol. 28, 1940, pp. 306-322, published bythe American Society for Metals, Cleveland, Ohio.

Tool Steels, Gill et al., p. 383, 1944, published by the AmericanSociety for Metals, Cleveland, Ohio.

